I am posting this for a friend of mine.mhe just bought a used 2007 f250 with the 6.0 power stroke. The truck has approx. 160,000 miles on it. He is having a issue with the truck overheating when it is cold out. When the air temp is above 30 degrees or so, he doesn't have a issue. So,my he overheating only occurs when driving down the highway in low temperatures. It can idle in the cold fine. Does anyone have any advice for me to point him in the right direction?

 

change the thermostat, change the water pump. These pumps have plastic fins and seem to crack, allowing the fins to not spin as fast as the shaft. He may consider cleaning the radiator of bugs, flush some water through the reverse direction.

 

The thing that I don't understand is it only overheats when the outside air temp is cold. If it was a cooling system problem like you explained, wouldn't it overheat all the time when driving? Another one of my friends suggested it could be the head gasket.

 

Lets think for a minute.

Overheats only when cold out, turn on heater, blows hot air or not?

What are the actual temps he's getting, not the dash gauge, that's for dummies. Scan Gauge II or Torque Pro reading from the OBD port?

Overheats only when driving.. fan speeds up during driving, water pump fins cracked and are not really matched to the pumps shaft anymore... pump spins faster but the fins don't because the fins are slipping, doesn't move more water and circulation dies... overheat.

At idle, pump doesn't turn fast, no load or heat build-up.. trucks good. It's really not forcing any water flow... just coasting along.

Overheat and coolant comes out the degas cap... that what were judging as overheat? That would coincide with head gaskets or possibly... but really over-pressurization of the coolant system, it will blow coolant out the cap. Getting on the throttle will cause it to happen faster... add a pressure gauge to the coolant return line just before it goes back into the degas tank. If it sees more than 16psi in a pretty short time, head gaskets are a real probability. Get a new de-gas cap first, gauge second... big pressure fast... ARP studs are coming soon!

Thermostat stuck shut (should fail open, maybe not), don't need much flow UNTIL we speed up and then its restricting the flow we need to effectively cool the truck.

EGR delete? Is the EGR valve plugged in... it provides the fan the desired fan RPM to cool the truck at certain temperatures... without an EGR sensor to control fan speed, it never comes up to speed... idles fine, fan turns at low speed. But if the fan doesn't cool the truck as required during high speed... over heat.

Does the fan kick into high gear when the trucks hot? it should sound like a turbo prop plane... really loud fan noise you can hear a mile away.

Fan clutch could be shot, can he turn it by hand? Any of the wires feeding the fan look damaged (they are right there and easy to access)?

Could be several things... have him answer what we thought of and go from there. Be very careful.. an over heated truck can have serious consequences on the motor..
Melted oil stand pipe, cracked heads/block due to heat...

a buddy of mine had a water pump go out and it over heated before he realized what happened... he had no gauges for live data and the dummy dash gauge just sat there.... cost him $8,000, that was a cheap rebuild!

 

I got some more info today from my friend. He says that when he has the heat on, suddenly the heat will start blowing cold air and that is when he knows it is going to overheat. He also says that when this happens, the truck starts running ****ty and he starts to get white exhaust out of the tailpipe.
Does this help any?

 

Does he have any gauges to monitor water and oil temps? What exactly is happening? Spewing out the degas bottle? Or is it just the temp guage on the dash maxing out? If you can get answers to watsons questions, he will narrow it down pretty quick I bet.

 

Is the coolant weak and freezing in the rad at highway speeds? I had that truck come in that cracked the block n it's stuck in my mind. Lol

 

normally trucks that sit at idle, heat starts blowing cold air and then the degas overflows.... isn't overheating... it's blowing the coolant out the cap because it's pressurizing the tank. AS is the head gaskets are the issue...

tell your buddy he needs to get a live gauge on the truck to see what temps its overheating at, before he cause more damage and he doesn't hydro lock the truck.

Have him check the oil level as well.

 

I agree with the coolant being questionable. Had a snowmobile do the same thing. Got real cold it overheated. Checked the lines and they were full of slush.

Diesel won't overheat idling.